Which term indicates whether a vapor is likely to rise or stay close to the ground?

• A. Vapor density
• B. Vapor pressure
• C. Vapor velocity
• D. Vapor concentration

Answer: (A)

Vapor density is the measure of how heavy a vapor is compared with air. If a vapor’s density is greater than air, it tends to stay near the ground and can pool in low-lying areas or shut-in spaces. If it’s lighter than air, it will rise and disperse upward. This is why the term that indicates whether a vapor is likely to rise or stay close to the ground is vapor density. Vapor pressure describes how readily a substance evaporates, not where the vapor will travel vertically. Vapor velocity refers to how fast the vapor plume moves, not its tendency to pool at floor level. Vapor concentration is about how much vapor is present in the air, not its vertical behavior.